1. Field of the Invention
The present invention relates to a hydrogen separation membrane with a carrier, to a fuel cell and a hydrogen separation apparatus having same, and to a method of manufacturing same.
2. Description of Related Art
A fuel cell is an apparatus that obtains electrical energy, generally using hydrogen and oxygen as fuel. Because the fuel cell is superior with regard to the environment and also achieves a high energy efficiency, fuel cell development is being widely pursued as a future energy supply system.
Of fuel cells, those that use a solid electrolyte include a solid polymer fuel cell, a solid oxide fuel cell, and a hydrogen separation membrane cell and the like. The term hydrogen separation membrane fuel cell is used herein to mean a fuel cell having a densified hydrogen separation membrane. A densified hydrogen separation membrane is a layer that is formed by a hydrogen-permeable metal, and that functions also as an anode. A hydrogen separation membrane cell has a structure in which a proton-conductive electrolyte is laminated onto a hydrogen separation membrane. Hydrogen that is supplied to the hydrogen separation membrane is converted to protons, which migrate within the proton-conductive electrolyte and bond with oxygen at the cathode, so as to generate electricity in the hydrogen separation membrane cell.
The hydrogen separation membrane used in the hydrogen separation membrane cell uses a precious metal such as palladium. For this reason, in order to reduce cost, it is necessary to make the hydrogen separation membrane as thin as possible. In this case, it is necessary to strengthen the hydrogen separation membrane by providing a carrier sheet of stainless steel or the like, and also to make the hardness of the hydrogen separation membrane high. There was a disclosure of art, in Japanese Patent Application Publication No. JP-A-2003-95617, for making a diffusion joining between a hydrogen separation membrane and a carrier sheet. According to this art, the hydrogen separation membrane and the carrier sheet are fixed together by joining. Because there is no melting of the base material, it is possible to make the overall apparatus thin.
When using the above-noted art, however, it is necessary to heat the hydrogen separation membrane and the carrier sheet when performing diffusion joining. In this case, because of the difference in the thermal coefficients of expansion between the hydrogen separation membrane and the carrier sheet, there may be occurred damage to the hydrogen separation membrane. It is possible to envision joining the hydrogen separation membrane and the carrier sheet by the cold joining method, such as the cladding method or the like. However, it is difficult for a hydrogen separation membrane with a high hardness to be deformed. As a result, there is a loss in the adhesion of contact between the hydrogen separation membrane and the carrier sheet.